Our lab discovered RTN-4B (called Nogo-B) as a protein highly abundant in endothelial cells (EC) and vascular smooth muscle (VSM) cells and mice deficient in Nogo-B have accelerated neointima after vascular injury, defective wound healing and impaired blood flow recovery post-ischemia. In exciting, preliminary data, we show that Nogo-B in the endothelium regulates the acute inflammatory response and neutrophil transmigration in vitro and in vivo. Mechanistically, the loss of Nogo suppresses ICAM-1 mediated signaling and the phosphorylation of VE cadherin in EC, which contributes to reduced inflammation in mice lacking Nogo-B. In a separate series of experiments examining the intracellular function of NgBR, we have discovered that in addition to binding Nogo-B, NgBR is critical for regulating intracellular cholesterol metabolism by stabilizing the Niemann Pick C2 protein (NPC2), raising the possibility that Nogo-B/NgBR signaling exerts a fundamental role in basic aspects of cholesterol homeostasis. In order to understand the integrated role of NgBR, we have generated conditional knockout mice and will examine its role in several experimental vascular paradigms that are impaired in Nogo-A/B KO mice. Thus, we hypothesize that Nogo-B and NgBR function as a novel endogenous regulatory system that coordinates the response to vascular injury or tissue ischemia and regulates endoplasmic reticulum (ER) functions such as cholesterol metabolism via stabilization of NPC2. In this proposal we will: 1. Define how Nogo-B regulates leukocyte transendothelial migration and vascular inflammation; 2. Examine Nogo-B regulation of NgBR mediated stabilization of NPC2 and cellular cholesterol metabolism; and 3. Characterize conditional NgBR knockout mice. Overall, the central goal of this proposal is to broadly understand the functions of Nogo-B as a prototypical reticulon family member and to examine its functions as a regulator of vascular homeostasis. PUBLIC HEALTH RELEVANCE: This research is relevant to public health since inflammation is a common manifestation of most cardiovascular diseases. Our research has discovered a new modulator of blood vessel function and remodeling during atherosclerosis or hypertension. Research supported by this grant may help identify new drugs that reduce heart disease and improve the quality of life of people suffering with cardiovascular disease.